1. Field of the Invention
The present invention relates to a valve assembly adapted to be attached to a gas cylinder containing a compressed gas and a liquefied gas for use in taking out and charging the gas and, more specifically, to a valve assembly enabling to take out a high-pressure gas within a gas cylinder from a gas outlet in a pressure-reduced state through a pressure reducing valve when the gas is taken out and to charge a high-pressure gas into the gas cylinder from the gas outlet when the gas is charged.
2. Description of the Prior Art
Among such valve assemblies, there is a one having the following construction as disclosed in the Japanese Patent Publication JPA 3-219172 which was proposed formerly by one of the inventors of the present invention.
Between a gas inlet and a gas outlet within a valve casing, a pressure reducing valve is disposed in series relative to a stop valve while a gas charging passage is provided in parallel relative to the pressure reducing valve. The gas charging passage is provided with a bypass check valve which serves to block a flow from the gas inlet to the gas outlet. A secondary safety valve is connected to an outlet of the pressure reducing valve and is provided with a backup pusher member.
The above-mentioned valve assembly is used as follows at the time of gas charging.
Prior to the gas charging working, a backup for the secondary safety valve is applied by the pusher member so as to prevent a blowout of the gas from the secondary safety valve which might be caused by a net pressure of the high-pressure gas to be charged. Then, the high-pressure gas is supplied to the gas outlet under an open condition of the stop valve. Thereupon, the high-pressure gas is supplied from the gas outlet to the gas cylinder through the bypass check valve and the gas inlet in order. After completion of the gas charging working, the backup for the safety valve is released.
Now, since such valve assemblies are necessarily fabricated in a compact structure corresponding to a size of the gas cylinder, also the secondary safety valve is made as small as possible.
At the time of gas charging, since it is necessary that an operator carries out the backup operation and the backup releasing operation of the small safety valve by his or her fingers, those operations are so difficult that the gas charging working takes much trouble. When the operator having gloves on effects the working, that problem becomes a great abuse because his or her fingers can't move freely.
Further, when the operator forgets the backup releasing operation by mistake after completion of the gas charging, the secondary safety valve doesn't work at the time of taking out the gas.